This invention generally relates to balloon catheters, particularly balloon catheters for deploying stents, such as after percutaneous transluminal coronary angioplasty (PCTA) procedures.
In a typical PTCA procedure a dilatation balloon catheter is advanced over a guidewire to a desired location within the patient""s coronary anatomy where the balloon of the dilatation catheter is properly positioned within a stenosis to be dilated. The balloon is inflated with radiopaque liquid at relatively high pressures (generally greater than 4 atmospheres) to dilate the stenosed region of the diseased artery. One or more inflations may be needed to effectively dilate the stenosis. The catheter may then be withdrawn from the stenosis or advanced further into the patient""s coronary anatomy to dilate additional stenoses.
Very frequently the PTCA treatment modality includes the placement of a stent either simultaneously during the angioplasty or after a dilatation of a stenotic arterial region has been completed to provide long term lumen patency. Balloon catheters similar to those described above for dilatation are used to deploy stents within a patient""s body lumen. Typically, an expandable stent is first disposed about the exterior of the deflated balloon on the distal extremity of the catheter in a constricted or otherwise unexpanded condition and then the catheter is advanced within the patient""s body lumen until the stent mounted on the exterior of the balloon is at the location in which the stent is to be deployed, e.g. at the stenotic site of a previous dilatation. The balloon is inflated so as to expand the constricted or otherwise unexpanded stent against the wall defining the body lumen and then the balloon is deflated and the catheter withdrawn from the patient""s body lumen. The expanded stent remains at the lumen site in an expanded condition when the catheter is removed.
Advances in material development for relatively non-compliant balloons designed for both dilatation and stent deployment have increased the tensile strength of the balloons allowing thinner balloon walls and thus lower catheter profiles. However, to obtain the benefits of a lower catheter profile, the wings which form when such balloons are deflated are wrapped around the inner member which extends through the interior of the balloon. The wrapped balloon may be covered with a protective sheath at least for handling and storage. Frequently, for stent delivery balloons, the stent is crimped onto a protective sheath covering which is somewhat elastically expansive so as to provide a more uniform expansion of the stent mounted on the sheath. The wrapped wings of the balloon are usually heat set in this condition so that the wings have a memory of the small wrapped dimensions when the balloon is deflated after inflation, e.g. for prepping, dilatation or stent deployment.
While some improvement in balloon profile has been obtained with the prior wrapped balloons, the procedures for forming the balloon with the desired memory complicates the manufacturing procedure and the use of the balloon. What has been needed is a catheter structure which simplifies the wrapping and eliminates the folding of the balloon wings and the heat setting thereof. The present invention satisfies these and other needs.
This invention is directed to a catheter having a balloon on a distal extremity of the catheter shaft which has a plurality of biased wings and to the method of forming the biased wings on the balloon.
The inflatable balloon on the catheter of the invention generally has a plurality of canted wings, each of which have been formed so as to be inclined at an angle of about 15xc2x0 to about 75xc2x0, preferably about 30xc2x0 to about 60xc2x0, with respect to a tangent line extending from the exterior of an inner member about which the wings are wrapped. The wings are formed of the cylindrical and part of the tapered ends of the balloon thus significantly reducing the balloon profile.
The inclined or canted wings are formed by pressing suitable shaping tools against the exterior of the balloon while the balloon is inflated at relatively low pressures of about 5 to about 20 psi, preferably about 8 to about 15 psi and, once the wings have been formed by the shaping tool, the interior of the balloon is subjected to a partial vacuum, i.e. a pressure of about 10 to about 29 inches (25.4-73.7 cm) of Hg, preferably about 20 to about 27 inches (51-68.6 cm) of Hg. in order to maintain the balloon in the constricted deflated condition with the canted wings of the balloon inclined and partially wrapped. The canted wings can be more easily wrapped around an inner tubular member extending within the balloon interior to reduce the effective profile of the balloon. The wrapping may be performed manually or by placing the balloon within an appropriate die and rotating either the balloon or the die or both to wrap the wings. A variety of other methods may be employed to wrap the balloons.
The vacuum applied within the balloon interior holds the canted wings in a wrapped position long enough so that a sheath or a stent can be mounted about the wrapped wings of the balloon. A stent may also be slid over and crimped onto the sheath for subsequent deployment. The angularity of the wings with respect to a line tangent to the exterior of the inner member greatly facilitates the wrapping of the wings and the reforming thereof when the deflated balloon is pulled back into a sheath or the distal end of a guiding catheter.
Details of stents suitable for use with the present invention can be found in U.S. Pat. No. 5,344,426, U.S. Pat. No. 5,423,885, U.S. Pat. No. 5,441,515, U.S. Pat. No. 5,443,458, U.S. Pat. No. 5,443,500 and U.S. Pat. No. 5,514,154, all of which are assigned to the present assignee. They are incorporated herein by reference. Other stent designs may also be employed.
In one aspect of the invention, the catheter has an elongated shaft with a proximal end, a distal end, a port in the distal end and guidewire lumen extending through at least the distal portion of the catheter to and in fluid communication with the port in the distal end of the catheter shaft. The balloon of the invention may be mounted on a distal extremity of the catheter shaft in a conventional fashion with a distal skirt secured by fusion bonding or a suitable adhesive to a distal extremity of the inner tubular member extending through the interior of the balloon and a proximal skirt of the balloon is similarly secured to a portion of the catheter shaft which may be the distal extremity of an outer tubular member which in part forms the catheter shaft.
The balloon may be made from suitable thermoplastic polymeric materials including high density polyethylene, polyethylene terephthalate (PET), polyamide (e.g. nylon 11 or 12), ionomers such as Surlyn sold by DuPont, polyurethane and polyamide block co-polymers such as PEBAX.
The present invention provides an intralumenal catheter with an improved balloon member with multiple wrapped wings which are formed so as to be inclined to predispose the wings to wrapping and subjected to an interior vacuum to hold the wings in the constricted condition. The crease which forms with the wing formation extend well into the tapered ends of the balloon which facilitates mounting a sheath or stent onto the wrapped balloon. A stent may be mounted and then crimped directly onto the wrapped balloon or onto a sheath covering the wrapped balloon for vascular deployment. The inclined wings also facilitate the pullback of the deflated balloon after a vascular or other procedure into the distal tip of the guiding catheter.
Long term disposition of the balloon in the wrapped condition and/or thermal treatment of the wrapped balloon effect a set which the balloon tends to stay in for the duration of storage and use.
These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings.